1. Field
The present invention relates to a steel piston having cooling channel without flash, and more particularly to the steel piston having cooling channel without flash which improves a cooling efficiency of the piston by deleting flash formed inside of an oil gallery during friction welding, preventing from forming of carbide, and improving a fluidity of oil inside of the oil gallery.
2. Description of the Related Art
A recently developed engine is aimed to have improved fuel economy, and to have high output and light weight to overcome environmental regulations, and it is seriously necessary to develop a steel piston to invent a high output and downsized engine as a next generation engine.
Also, a piston which is a key component of the next generation engine should endure high combustion and temperature, particularly, it is absolutely necessary to improve a cooling efficiency of the piston because a fatigue property and density of the material in a high temperature are decreasing.
However, as shown in FIG. 1, flash (3) is formed on an inner and an outer circumference surface of the oil gallery (2) of the conventional piston (1) during friction welding, and the flash formed on the inner circumference surface and the outer circumference surface of the oil gallery (2) incurs problem.
In other words, as said flash is formed on the inner and the outer circumference surfaces of the oil gallery (2) by friction welding, carbides get accumulated on the flash (3), and the oil fluidity is decreased by the oil, and therefore, the cooling efficiency of the piston, which is opposed to the technology aiming to improve the fatigue property and density of the piston as the main component of the next generation engine in the high temperature by improving the cooling efficiency.
Also, it has a problem of incurring cracking in the middle area of said flash (3) by a notch effect which is increasing of stress and becoming as the crack causing area (4).